Did all the simple car checks today, came to the oil, topped it up a little bit and noticed a thick brown sludge.
I've googled it and It seems it can be water in the oil from driving like a granny or short journeys (I do a fair few of them)
or a bust thermostat?
Any other checks I can run to make sure my heads not about to blow. Not had to top up oil in months and I've done a lot of miles, still plenty of coolant.